XmlDsigXPathTransform Constructor

public:
 XmlDsigXPathTransform();

public XmlDsigXPathTransform();

Public Sub New ()

Examples

The following code example shows how to sign and verify an XML document using the XmlDsigXPathTransform class. This example creates an envelope signature.

//
// This example signs an XML file using an
// envelope signature. It then verifies the
// signed XML.
//
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;

public class SignVerifyEnvelope
{

    public static void Main(String[] args)
    {
        // Generate a signing key.
        RSA Key = RSA.Create();

        try
        {
            // Create an XML file to sign.
            CreateSomeXml("Example.xml");
            Console.WriteLine("New XML file created.");

            // Sign the XML that was just created and save it in a
            // new file.
            SignXmlFile("Example.xml", "SignedExample.xml", Key, "ancestor-or-self::TempElement");
            Console.WriteLine("XML file signed.");

            // Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...");
            bool result = VerifyXmlFile("SignedExample.xml");

            // Display the results of the signature verification to \
            // the console.
            if (result)
            {
                Console.WriteLine("The XML signature is valid.");
            }
            else
            {
                Console.WriteLine("The XML signature is not valid.");
            }
        }
        catch (CryptographicException e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            Key.Clear();
        }
    }

    // Sign an XML file and save the signature in a new file.
    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key, string XPathString)
    {
        // Create a new XML document.
        XmlDocument doc = new XmlDocument();

        // Format the document to ignore white spaces.
        doc.PreserveWhitespace = false;

        // Load the passed XML file using it's name.
        doc.Load(new XmlTextReader(FileName));

        // Create a SignedXml object.
        SignedXml signedXml = new SignedXml(doc);

        // Add the key to the SignedXml document.
        signedXml.SigningKey = Key;

        // Create a reference to be signed.
        Reference reference = new Reference();
        reference.Uri = "";

        // Create an XmlDsigXPathTransform object using
        // the helper method 'CreateXPathTransform' defined
        // later in this sample.

        XmlDsigXPathTransform XPathTransform = CreateXPathTransform(XPathString);

        // Add the transform to the reference.
        reference.AddTransform(XPathTransform);

        // Add the reference to the SignedXml object.
        signedXml.AddReference(reference);

        // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        KeyInfo keyInfo = new KeyInfo();
        keyInfo.AddClause(new RSAKeyValue((RSA)Key));
        signedXml.KeyInfo = keyInfo;

        // Compute the signature.
        signedXml.ComputeSignature();

        // Get the XML representation of the signature and save
        // it to an XmlElement object.
        XmlElement xmlDigitalSignature = signedXml.GetXml();

        // Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, true));

        // Save the signed XML document to a file specified
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false));
        doc.WriteTo(xmltw);
        xmltw.Close();
    }
    // Verify the signature of an XML file and return the result.
    public static Boolean VerifyXmlFile(String Name)
    {
        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Format using white spaces.
        xmlDocument.PreserveWhitespace = true;

        // Load the passed XML file into the document.
        xmlDocument.Load(Name);

        // Create a new SignedXml object and pass it
        // the XML document class.
        SignedXml signedXml = new SignedXml(xmlDocument);

        // Find the "Signature" node and create a new
        // XmlNodeList object.
        XmlNodeList nodeList = xmlDocument.GetElementsByTagName("Signature");

        // Load the signature node.
        signedXml.LoadXml((XmlElement)nodeList[0]);

        // Check the signature and return the result.
        return signedXml.CheckSignature();
    }

    // Create the XML that represents the transform.
    private static XmlDsigXPathTransform CreateXPathTransform(string XPathString)
    {
        // Create a new XMLDocument object.
        XmlDocument doc = new XmlDocument();

        // Create a new XmlElement.
        XmlElement xPathElem = doc.CreateElement("XPath");

        // Set the element text to the value
        // of the XPath string.
        xPathElem.InnerText = XPathString;

        // Create a new XmlDsigXPathTransform object.
        XmlDsigXPathTransform xForm = new XmlDsigXPathTransform();

        // Load the XPath XML from the element.
        xForm.LoadInnerXml(xPathElem.SelectNodes("."));

        // Return the XML that represents the transform.
        return xForm;
    }

    // Create example data to sign.
    public static void CreateSomeXml(string FileName)
    {
        // Create a new XmlDocument object.
        XmlDocument document = new XmlDocument();

        // Create a new XmlNode object.
        XmlNode node = document.CreateNode(XmlNodeType.Element, "", "MyXML", "Don't_Sign");

        // Append the node to the document.
        document.AppendChild(node);

        // Create a new XmlNode object.
        XmlNode subnode = document.CreateNode(XmlNodeType.Element, "", "TempElement", "Sign");

        // Add some text to the node.
        subnode.InnerText = "Here is some data to sign.";

        // Append the node to the document.
        document.DocumentElement.AppendChild(subnode);

        // Save the XML document to the file name specified.
        XmlTextWriter xmltw = new XmlTextWriter(FileName, new UTF8Encoding(false));
        document.WriteTo(xmltw);
        xmltw.Close();
    }
}

'
' This example signs an XML file using an
' envelope signature. It then verifies the 
' signed XML.
'
Imports System.Security.Cryptography
Imports System.Security.Cryptography.X509Certificates
Imports System.Security.Cryptography.Xml
Imports System.Text
Imports System.Xml



Module SignVerifyEnvelope


    Sub Main(ByVal args() As String)
        ' Generate a signing key.
        Dim Key As RSA = RSA.Create()

        Try
            ' Create an XML file to sign.
            CreateSomeXml("Example.xml")
            Console.WriteLine("New XML file created.")

            ' Sign the XML that was just created and save it in a 
            ' new file.
            SignXmlFile("Example.xml", "SignedExample.xml", Key, "ancestor-or-self::TempElement")
            Console.WriteLine("XML file signed.")

            ' Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...")
            Dim result As Boolean = VerifyXmlFile("SignedExample.xml")

            ' Display the results of the signature verification to \
            ' the console.
            If result Then
                Console.WriteLine("The XML signature is valid.")
            Else
                Console.WriteLine("The XML signature is not valid.")
            End If
        Catch e As CryptographicException
            Console.WriteLine(e.Message)
        Finally
            Key.Clear()
        End Try

    End Sub


    ' Sign an XML file and save the signature in a new file.
    Sub SignXmlFile(ByVal FileName As String, ByVal SignedFileName As String, ByVal Key As RSA, ByVal XPathString As String)
        ' Create a new XML document.
        Dim doc As New XmlDocument()

        ' Format the document to ignore white spaces.
        doc.PreserveWhitespace = False

        ' Load the passed XML file using it's name.
        doc.Load(New XmlTextReader(FileName))

        ' Create a SignedXml object.
        Dim signedXml As New SignedXml(doc)

        ' Add the key to the SignedXml document. 
        signedXml.SigningKey = Key

        ' Create a reference to be signed.
        Dim reference As New Reference()
        reference.Uri = ""

        ' Create an XmlDsigXPathTransform object using 
        ' the helper method 'CreateXPathTransform' defined
        ' later in this sample.
        Dim XPathTransform As XmlDsigXPathTransform = CreateXPathTransform(XPathString)

        ' Add the transform to the reference.
        reference.AddTransform(XPathTransform)

        ' Add the reference to the SignedXml object.
        signedXml.AddReference(reference)

        ' Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        Dim keyInfo As New KeyInfo()
        keyInfo.AddClause(New RSAKeyValue(CType(Key, RSA)))
        signedXml.KeyInfo = keyInfo

        ' Compute the signature.
        signedXml.ComputeSignature()

        ' Get the XML representation of the signature and save
        ' it to an XmlElement object.
        Dim xmlDigitalSignature As XmlElement = signedXml.GetXml()

        ' Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, True))

        ' Save the signed XML document to a file specified
        ' using the passed string.
        Dim xmltw As New XmlTextWriter(SignedFileName, New UTF8Encoding(False))
        doc.WriteTo(xmltw)
        xmltw.Close()

    End Sub

    ' Verify the signature of an XML file and return the result.
    Function VerifyXmlFile(ByVal Name As String) As [Boolean]
        ' Create a new XML document.
        Dim xmlDocument As New XmlDocument()

        ' Format using white spaces.
        xmlDocument.PreserveWhitespace = True

        ' Load the passed XML file into the document. 
        xmlDocument.Load(Name)

        ' Create a new SignedXml object and pass it
        ' the XML document class.
        Dim signedXml As New SignedXml(xmlDocument)

        ' Find the "Signature" node and create a new
        ' XmlNodeList object.
        Dim nodeList As XmlNodeList = xmlDocument.GetElementsByTagName("Signature")

        ' Load the signature node.
        signedXml.LoadXml(CType(nodeList(0), XmlElement))

        ' Check the signature and return the result.
        Return signedXml.CheckSignature()

    End Function


    ' Create the XML that represents the transform.
    Function CreateXPathTransform(ByVal XPathString As String) As XmlDsigXPathTransform
        ' Create a new XMLDocument object.
        Dim doc As New XmlDocument()

        ' Create a new XmlElement.
        Dim xPathElem As XmlElement = doc.CreateElement("XPath")

        ' Set the element text to the value
        ' of the XPath string.
        xPathElem.InnerText = XPathString

        ' Create a new XmlDsigXPathTransform object.
        Dim xForm As New XmlDsigXPathTransform()

        ' Load the XPath XML from the element. 
        xForm.LoadInnerXml(xPathElem.SelectNodes("."))

        ' Return the XML that represents the transform.
        Return xForm

    End Function


    ' Create example data to sign.
    Sub CreateSomeXml(ByVal FileName As String)
        ' Create a new XmlDocument object.
        Dim document As New XmlDocument()

        ' Create a new XmlNode object.
        Dim node As XmlNode = document.CreateNode(XmlNodeType.Element, "", "MyXML", "Don't_Sign")

        ' Append the node to the document.
        document.AppendChild(node)

        ' Create a new XmlNode object.
        Dim subnode As XmlNode = document.CreateNode(XmlNodeType.Element, "", "TempElement", "Sign")

        ' Add some text to the node.
        subnode.InnerText = "Here is some data to sign."

        ' Append the node to the document.
        document.DocumentElement.AppendChild(subnode)

        ' Save the XML document to the file name specified.
        Dim xmltw As New XmlTextWriter(FileName, New UTF8Encoding(False))
        document.WriteTo(xmltw)
        xmltw.Close()

    End Sub
End Module